This invention relates to vehicle service apparatus and more particularly to wheel alignment and diagnostic apparatus utilizing ride height measurements.
The ride height of a vehicle may be defined in various ways. Some manufacturers specify ride height as the distance from the ground to the vehicle bumper, while others may use the distance between the center of a wheel (or some other reference point) and the vehicle body wheel arch for that wheel. No matter how defined, the ride height typically changes over time. These changes can result from wear of or damage to the suspension components or incorrect adjustment, and can be evidence of serious alignment problems. Or they may merely reflect the action of adjustable suspensions or variations in load. Some manufacturers provide specifications for ride height which, if ignored, can result in failure to adequately diagnose and repair misalignment of the vehicle. Moreover, changes in measured alignment angles with ride height may evidence serious problems such as bump steer, improper cradle adjustment, or extremely worn or loose parts.
U.S. Pat. No. 4,977,524 to Strege et al. (co-assigned with the present application) discloses an electronic measuring gauge for measuring ride height which supplies the measured ride height to a vehicle inspection/alignment system. That electronic measuring gauge was hand held by the technician/user and was connected by a separate cable to the inspection/alignment system console. The console included a computer with a memory which compared the measured ride height from the hand held measuring gauge with stored specifications for ride height.
For some time, it has been known that caster measurements for light trucks are affected by ride height, specifically by the frame angle calculated from front and rear ride height measurements. Printed charts have been provided for use by the technician to manually compensate for ride height in that particular situation.